Process for grading abrasives



F. GELSTHARP PROCESS FOR GRADING ABRASIVES Dec, 16, 1&24.

Filed June 23, 1921 Patented Dec. 16,1924.

UNITED STATES PATENT OFFICE.

FREDERICK GELSTHARP, OF TARENTUM, PENNSYLVANIA, ASSIGNOR TO PITTSBURGH PLATE GLASS COMPANY, A CORPORATION OF PENNSYLVANIA.

PROCESS FOR GRADING ABRASIVES.

Application filed June 23-, 1921. Serial No. 479,855.

To all whom it may concern:

Be it known that I, FREDERICK GELSTHARP, a citizen of Great Britain, and a resident of Tarentum, in the county of Allegheny and State of Pennsylvania, have made a new and useful invention in Imprpvements in Processes for Grading Abrasives, of which the following is a specification.

This invention relates to the grading of abrasives particularly for use in giving plate glass what is known as its smooth after the ordinary coarse grinding operation with sand of varying degrees of fineness. It will be understood, however, that the abrasive secured by the iniproved process may be used in other industrial operations aside from the grinding or smoothing of glass.

For producing the smoothing action on plate glass preliminary to polishing, it has been heretofore the practice to employ emery which, is a product produced in natureand ground to varying degrees of fineness. The emery is separated into several grades by a water grading operation and these are used successively from the coarsest to the finest,

- thus reducing the glass surface to a relatively high degree of smoothness. The degree of smoothness has been limited, however, by inability to secure the very finest grades of emery in the mass which is graded. There is a tendency of the finest particles to flocculate or adhere together or to larger particle s, which, of course, prevents their separation from the coarser grades. I

The purpose of the present invention is to provide a process whereby the tendency of the finer grades to flocculate or adhere is prevented to the end that such particles may be collected in a separategrade or series of grades finer than those heretofore collected.

Further objects are to-secure a more complete separation from the abrasive of mud or other non-abrasive material, and to secure a cleaner and more accurate separation of t the coarser grades.

' very fine abrasives'designed for a similar While the invention may be utilized to advantage in the grading of emery, which is the abrasive generally employed in securing a smooth upon plate glass, I have found that it maybe used to advantage with other use, during the grading operation, of a separating or defiocculating agent which has the effect of causing the fine particles to separate fromeach other and from the larger "particles so that the grading action of the liquid may be effective to produce a separation which will bring into the same'grade those particles which are of the same size, and so that the finer grades will not be carried down by the coarse. The best agent so far found is gum ara-bic, altho a number of other substances, such as glue and ammonia, have a similar effect when used in somewhat larger quantities, but are greatly inferior in accomplishing the result desired, and because of the objectionable odor. I have found the quantityof gum arabic may be varied within certain limits, depending upon conditions,

but that the best results are secured when the gum arabic constitutes about one-half to two per cent by weight of the carborundum or alundum being graded. Too much of the agent causes the graded material to settle into a hard mass. The deflocculator is added to the mixture of water and abrasive previous to grading, preferably in the mixing chamber, so that it is effective throughout the grading in all the successive cans.

The apparatus for grading the abrasive as generally used comprises the mixing container and a series of ten or twelve cans of increasing cross sectional area, the arrangement being shown in the accompanying drawings in which;

The figure is a diagrammatic sectional view of a part only of the series of cans, the rest of the' series being similarly constructed and arranged. a

In starting the operation the emery and water are mixed in the-tank 1, together with the gum arabic, which is to give the deflocculating or separating function heretofore explained. The liquid is then allowed to escape through the outlet 2, and from this outlet it flows through the trough '3 to the pipe 4: provided at its upper end with the funnel 5. The pipe 4 leads to a point adja cent the bottom of the first can 6, suchcan and the succeeding cans 7, 8, 9, etc. being filled to the level indicated, with clear. water. The overflows from the various cans pass successively to the pipes 10, 11 and 12, which pipes are provided with the funnel upper ends similar to that of the pi e 4. Coincident with the flow o the mixture of the abrasive and water from the tank 1,

a supply of water is also provided through the pipe 13, and the flow fromthe tank 1" h is continued until the mixture is completely withdrawn. As the flow from theoutlet 2 decreases the flow.of water I'rom the pipe 13' is increased, so that at the end of the operation only clear water is flowing throu h the trough 3 into the pipe member '4, an this flow is continued. until the grading in the cans is completed. The purpose in increasing the fiow through the pipe 13 as the flow through the pipe 2 decreases is to maintain the downward flow through the pipe 4, and, infact, through the entire system uniform, so that the grading action due to the upward flow of the water in the various cans is uniform. The supplying of the liquid through the pipe members 4, 10, 11, 12, etc., gives an upward flow through each of the cans, and as these cans are of increasing size, the velocity of upward flow in each succeeding can is less. As a result the first-can retains the coarsest abrasive and each succeeding can a finer grade.

The grades retained'in the first cans are too coarse for use in smoothing, and after' the completion of the operation are removed and reground, but the grades collected in the final four or five cans are of the requisite degree of fineness. for use and are removed and used'in the grinding operation'in the separate from each other, so that the amount of the finer grades which are carried down by the coarser articles in the first cans of the series, is re need to a minimum. As a result, the amount of the finer grades collected in the final cans is increased, but still more important, the grading can be carried to a finer degree,jthat is, finer grades may be secured at the end of the operation due to the fact that the fine particles are separated instead of adherent to each other. By the use of these finer grades not obtainable without the use of the deflocculating agent, the smoothing operation with the abrasive can be carried much further than has heretofore been possible, and as a result, the final polishing operation with rouge can be accomplished more quickly, thus involving a saving of time .and power. For instance, it has been found possible to reduce the time of polishing glass, smoothed by these finer grades of emery, about forty per cent. The polishing operation is expensive by reason of the great amountof power re-' quired, and this decrease. in the time of pohshlng and the consequent power consumption involves great economy, even where a few minutes more time is consumed t e smoothing operation, as heretofore described. The application of these finer grades of abrasive as secured by the process herein set forth, may consume from five to ten minutes longer in this smoothing operation, but the power consumption per minute is much less than in'the polishing operation,

so that the total saving in power incident to the separation of the finer grades, which it has been heretoforeimpossible to utilize, involves in the, aggregate not only a saving of time in the total operation but a relatively greater saving in power required{ After the operation as heretofore dein applying' the finer grades of abrasive in scribed with the use of the--defiocculating agent has been carried as far as it is practical to carry it, there still remains in the overflow acertain amount of exceedingly fine abrasive mixed with mud, which mixture has heretofore been conducted to the sewer and thrown away. I have found that this material in suspension may be saved and collected by adding thereto what may be termed a flocculating agent,that isyan,

agent which performs a functionthe reverse of the defiocculating function and causes the particles of abrasive and mud to adhere to each other, thus forminglarge particles which can be settled and utilized. Annmber of substances can be used to accomplish this function, among which ma be mentioned common salt and alum. hese substances when added to the lastcan of the series cause a large proportion ofjthe material to settle, after which it may be removed and used as thefinal smoothing abrasive. This material contains impurlties in the form of mud which has no abrasive action, but the percentage of abrasive is suflicient to permit the use of the mixture as an abrasive, and the use of this abrasivegives a very fine finish to the glass so that the time of polishing may be still further cut down. i

The invention has been described in connection with the form of separator or grader illustrated, which is the one more commonly used in the plate glass art, but the invention is not limited to a grader or separator of this character, and is applicable to any separator in which the separation of the material into grades is accomplished by a flow of liquid upward through a body of liquid containing the particles of abrasive of varying size in suspension.

One of the other systems to which this feature of securin additional separation by the use. of a de occulator has been applied involves the use of a conical grader of relatively large size surrounded by or placed adjacent to a series of small cones from which the contents of the large cone is directed from the different levels thereof, such system being shown and described in the Hitchcock Patent No. 1,100,302 of June 16, 1914. An upward flow of liquid inthe large cone causes the different grades to collect in difl'erent strata, owing to the varying upward velocity through the cone, the larger particles accumulating near the bottom of the cone and the size of the particles decreasing from the bottom of the cone up. The various finer grades suitable for smoothing work are withdrawn into the smaller cones and subjected to a further grading action to remove any particles which were not properly graded in the initial operation. The material in the bottom of the large cone which is too coarse for use as a smoothing abrasive is withdrawn and reground as in the other' type of apparatus. The use of the deflocculator here accomplishes the same function as in connection with the other type of apparatus. The invention is obviously not limited to any particular type of apparatus, the principle being generally applicable where there is a water flow operation.

What I claim is: v

1. The process of grading inorganic abrasives consisting in subjecting a mass of abrasive to a liquid flow in the presence of a deflocculating ag nt and collecting sepgrades being of substantially the same composition.

2. The process of grading inorganic abrasives consisting in subjecting a mass of abrasive to an upward flow of liquid in the presence of a deflocculating agent and collecting separate size grades of the abrasive as suspended thereby, the grains of the different grades being of substantially the same composition.

. 3. The process of grading inorganic abrasives consisting in subjecting a mass of abrasive to a liquid flow in the presence or gum arabic as a deflocculating agent and collecting separate size grades oi the abrasive as suspended thereby, the grains of they diflerent grades being of substantially the same composition.

In testimony whereof, I have hereunto subscribed my name this 16th day of June, 1921.

FREDERICK GELSTHARP.

Witness:

;G.' C. DODSON. 

